Does a separate GPU for CUDA work with main AMD card, in Cycles?
Silly me, i completely forgot about the option in the renders tab, i thought the user settings was enough. Anyway it does appear to work, fur mark does show the GPU heating up.

It isn't very useful due to it's low memory and little processing power, but being on a separate GPU i can render lesser projects while doing other tasks.

I did NOT have to enable Experimental Feature Set. do not know if it changes anything.

Thanks everyone!